PT94802B - PROCESS FOR THE IMPROVEMENT OF THE SURFACE OF ARTICLES OF PLASTIC MATERIAL REFORCADO BY FIBERS. - Google Patents

Abstract

A granular filler, suitable for incorporating in a composition for use in coating the surface of a glass mat-reinforced thermoplastic material, characterised in that the granular filler comprises (a) a particulate inorganic material, (b) from 0.1% to 10% by weight, based on the weight of the inorganic material, of fine carbon black, and (c) sufficient of a natural or synthetic latex composition to provide from 1% to 10% by weight of elastomer, and in that the granules have diameters in the range from 0.01 mm to 0.1 mm. <IMAGE>

Description

DESCRIPTIVE MEMORY

The present invention relates to improving the surface of fiber reinforced articles.

process for plastic material

United States Patent No. 4,734 321 establishes a process for producing a permeable sheet-like material comprised of unconsolidated particulate plastics (especially thermoplastic materials, and relatively short reinforcing fibers, typically 50 millimeters or less in length) . After intermediate processing, in order for the plastic component to be brought to a molten state and to wet the reinforcing fibers completely, the material is suitable for molding into fiber-reinforced plastic articles. Various intermediate processing routes can be used.

Thus, for example, and as described in the aforementioned United States Patent, the permeable material can be subjected to heat and pressure and then cooled to form a consolidated sheet. Before use in a molding process, the sheet is reheated so that the plastic component softens and allows the stresses in the fiber reinforcement to relax and re-expand the sheet, which can then be molded into a mold.

The use of unique short fibers in the material has considerable advantages since, when subjected to mold, they flow readily with the thermoplastic are incorporated. This results in a distribution of fibers throughout the mold, giving a reinforcement to the entire molded structure, even in the most molded molds, there is pressure in the melt.

In the mold molding process, a charge of preheated material above the melting temperature of the plastic component is loaded into a mold in which the parts of the mold are controlled at a lower temperature than that at which the plastic component will solidify. Molding pressure is then applied to the hot filler quickly enough for the fiber and plastic filler components to flow into the mold configuration before the plastic component solidifies.

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-3 Molding in a mold is a well-known technique for molding non-reinforced plastic materials. However, it has been found that its use for molding plastic materials reinforced by short fibers may result in deterioration of the surface of the final mold. For different reasons, other types of fiber-reinforced thermoplastic materials may also suffer from surface defects due to the protrusion of the fiber.

The production process for the starting material, as set out in United States Patent NP. 4,734 321, causes the component fibers to orient themselves, generally, in the plane of the sheet. However, it has been found that when deterioration of the surface occurs during subsequent molding, it is caused by the projection of the fibers through the surface of the sheet.

Another form of fiber-reinforced plastic sheet is produced by laminating together, in a frame press, layers of glass fiber needle blanket and thermoplastic resin such as polypropylene. Methods used to produce such products are described in United States Patent Nos. 3,664,909, 3,664,645, 3,713,962 and 3,850,723. However, it has been found that the use of such sheets in molding in molds or coinage operations results in a slight protuberance of the fibers on the surfaces of the resulting mold, so that, on the surface, apparent visual irregularities occur.

Another system for forming fiber-reinforced plastic sheets is disclosed in United States Patent NP.

328 383, in which a mixture of glass and thermoplastic fibers is deposited on a flat surface and then consolidated by pressure after heating. Here again, subsequent molding of the consolidated sheet results in the overlapping of the sheet surface by the fibers.

Among the objects of the present invention is the improvement of the surface finish of moldings formed from sheets of the type described above.

According to the present invention, a process for preparing

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-4a permeable sheet of fiberglass-reinforced thermoplastic material for molding into a shaped product, includes attaching to the sheet a surface layer of particulate material which is compatible with or inert to the thermoplastic content of said sheet and which acts to improve the finishing of the sheet surface, when the sheet is subsequently heated and molded into a mold, under pressure.

The particulate material may be a mineral filler material, for example, a clay, carbon black or titanium dioxide, calcium carbonate, a thermoplastic, a hot-hardening plastic, an antioxidant material, a pigment, or a mixture of such materials. Alternatively, or in addition, inorganic fillers as described in, for example, International Patent Application (PCT) No. WO 88/006606 and United Kingdom Application No. 2 179 665 A.

The formation of a particulate surface coating has special advantages in terms of sheet handling when used with sheet materials like those disclosed in United States Patent No. 4,734 321. Because each particle is bonded individually, directly or indirectly, on the leaf surface, it does not interfere with the leaf's flexibility or, significantly, with its permeability. As a result, the sheet can be wound and reheated prior to molding by transmitting hot air through the sheet, as described, for example, in European Patent Application NO. 85.300033 (Publication No. 0 148 762).

Such particulate coatings also have advantages for use with other forms of fiber-reinforced plastic sheet. Thus, it was found that the use of a mineral filler material in the finishing layer, increases the viscosity of the plastic content of the sheet surface, so that it resists when the reinforcing fibers cross the surface. The use of plastic materials and particles in the surface finishing layer produces an enrichment of the plastic content on the surface, with the same result.

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-5The particle surface layer can be applied using various techniques. Thus, for example, an aqueous coating of a dispersion of the particulate material can be applied, in a conventional manner, to an aqueous coating. Alternatively, a surfactant can be added and the dispersion stirred under turbulent conditions to form a foam, the foam being then applied as a coating, as described in UK Patent No. 1,039,540 or US Patent United States NQ. 4 263 344.

Otherwise, the particulate material can be applied as a dry powder, by various techniques, as long as the process conditions are such as to ensure that the powder binds to the sheet.

An aqueous dispersion can be applied, with a water consistency of 0.5 to 30% (w / w) or 5 to 300 grams per liter of water. For a typical production speed of 7 meters per minute of sheet to be coated, the coating would be applied at a speed of 0.8 to 500 liters per minute per meter of sheet width.

A foam coating can be applied at a speed of between 50 and 500 grams per square meter, with a foam consistency of 0.5 to 10% (w / w) or 5 to 100 grams per liter of water. For an air content of 67% this is equivalent to 1.6 to 33 grams per liter of foam.

The sheet is coated at a typical production speed of 5 meters per minute, with the flow rate for the foam ranging from 8 to 4000 liters per minute per meter of sheet width.

Dry powders can be applied at a speed of grams per square meter for a typical speed of 7 square meters per minute.

to 500 production

In a known process for the production of glass fiber reinforced thermoplastic material, for sheet, a mixture of cut glass fibers, polypropylene powder and an inorganic filler material, such as kaolin, carbonate or calcium, talc, mica, titanium dioxide / sodium trihydrate

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-6alumina, is dispersed in water containing a surfactant (which can be anionic or non-ionic), using a high speed mixer, to form a stable foam, with a relatively low solids content. This foam is spread evenly over the surface of a moving wire mesh, as is conventionally used in a Fourdrinier paper making machine, and the aqueous phase is removed through the wire mesh by gravity and suction. The blanket of solid materials as well as the upper surface of the wire mesh is then at a temperature of about 100 ° C. The blanket, usually dried after being cut into pieces of suitable size and stacked to form a multilayer material for sheet, is pressed between steel plates at a temperature of about 200 ° C and then allowed to cool in the press, to form a component identical to a sheet, such as a panel for the body of a car.

formed in the drought to a resultant, can be

Alternatively, the stacks of the cut pieces heated to about 200 ° C by means of a hot air stream or by infrared radiation and subsequently allowed to cool in a press to about 60 ° C, to form a sheet-like material .

In addition to glass fibers, polypropylene and inorganic filler material, it is often necessary to include a small amount of carbon black in the starting mixture for the thermoplastic material reinforced by a fiberglass mat. about 4% by weight of the total solid material. (Carbon black is the ternium widely used to describe a range of fine, carbon products that can be made by partial combustion or thermal decomposition of hydrocarbons in vapor phase. The definitive colloidal units of carbon black can occur as aggregates, which are fused assemblies of particles up to 500 nanometers (most carbon blacks have an elemental carbon composition greater than 90%). Carbon black is introduced, not only to make the final sheet material black, as it is often needed in commerce, but also to provide a shielding effect against harmful action on the radiation material

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-7ultraviolet. However, when carbon black is introduced into the starting mixture, problems are experienced because of the well-known difficulties in handling fine carbon black powder without forming a cloud of black particles that will settle over a wide area. This problem is especially serious when mixing dry carbon black with dry thermoplastic. It was found that the retention

-carbon in the fiber, in the blanket ₍ during the wire mesh forming operation is poor, and it is generally believed that the carbon black is irregularly dispersed in the final pressed material and with the result of the sheet material have an appearance and speckled, with dark areas, having a concentration of charcoal black, alternating with areas that are colored a black-dry material, high light streak and almost translucent.

in the mixture by blanket of the

It is also often advantageous to include starting for the glass fiber reinforced thermoplastic material, from 0.1% to 10% by weight, based on the weight of the inorganic filler material, of an antioxidant.

GB-A-2 179 665 described a process for the preparation of an inorganic filler material, which process comprises treating an inorganic filler material in particles with a natural or synthetic latex composition, and removing the water and drying the mixture resulting. The inorganic filler material with the treated surface can be used, with polymeric resin composition.

advantage in a

It has now been found that an improved thermoplastic material reinforced by a fiberglass mat can be obtained if the mat of solid materials formed on the upper surface of the wire mesh of the Fourdrinier paper-making machine is coated with a composition comprising an aqueous suspension of a mixture of polypropylene powder, granules of inorganic filler material, a foaming agent and, optionally, additional natural or synthetic latex solids. It was found that when the thermoplastic material reinforced by a fiberglass mat, in the form of a pile of cut pieces, is pressed to

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-8 hot, as previously described, there is a tendency for the reinforcing glass fibers to be pushed across the surface of the sheet material giving a smooth, furry texture to the surface. However, if at least one side of each blanket is covered with a composition of the type described above, and a pile of cut pieces of blanket is prepared, so that on each side of the pile is a surface coated exterior, the surface of the pressed component, identical to the sheet, is effectively sealed so that the glass fibers are prevented from projecting through the surface.

A granular filler material for use in the present invention, suitable for incorporation into a composition for use in coating the surface of a thermoplastic material reinforced by a fiberglass mat, comprises (a) an inorganic particulate material (b) of 0, 1% to 10% by weight, based on the weight of the inorganic material, from fine carbon black, and (c) sufficient latex composition, natural or synthetic, to provide 1% to 10% by weight, of elastomeric solids, based on the weight of the inorganic material, and, where, the granules have diameters in the range of 0.01 mm to 0.1 mm.

A composition for use in coating the surface of a thermoplastic material reinforced by a fiberglass mat, according to the invention, comprises an aqueous suspension of a polypropylene powder, a granular filler material, according to said aspect of the invention. , and a foaming agent. Advantageously, the composition also includes latex solids, natural or synthetic, in addition to those present in the granular filler.

invention will be, reference to the drawings now, described eni more included here, in which:

detail with Figure 1 is an elevation of the section of a permeable, fiber-reinforced plastic material, surface layer in particles according to the sheet having an invention, Figure 2 is an elevation of the section of the sheet of Figure 1 after consolidation under pressure and heat,

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Figure 9 is an elevation of the section of another permeable fiber-reinforced plastic sheet according to the invention, Figure 4 is an elevation of the section of the sheet of Figure 3 after consolidation under pressure and heat, Figure 5 is a representation schematic of the sequence of operations in a process for the manufacture of a fiber-reinforced plastic material and in which a surface layer in particles, according to the invention, can be applied, Figures 6 to 9 are four semi-schematic elevations showing four different types of apparatus for forming permeable fiber-reinforced plastic material for sheet, according to the invention, Figures 10 to 12 are semi-schematic views showing various techniques for the distribution of dry particles over a web of material for sheet, Figure 13 is a schematic illustration of the continuous lamination process for producing fiber-reinforced plastic sheets.

Referring first to Figure 1, it shows a permeable material for sheet comprised of a substrate 2, made according to the process described in United States Patent NB. 4,734 321, to which a surface layer in particles 3 has been attached. When cooled, after being subjected to heat and pressure, in a molding process in a mold, a consolidated sheet or mold 4 is formed, as shown in figure 2, the molded 4 having a fiber reinforced base layer 5 and an unreinforced surface layer 6, the layers 5 and 6 being respectively derived from layers 2 and 3 of figure 1.

If desired, substrate 2 can be formed, alternatively, by dry deposition of a mixture of reinforcing fibers and thermoplastic material, as generally described in United States Patent No. 3. 3 328 383, the description of which is included here for reference, and then a layer in

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-10 particles to the resulting substrate, before heating until melting into a permeable structure.

Referring now to a sheet comprising which a material 9 of the fiber webs of Figure 3 has been extruded so as to connect them, this shows a structure of glass fiber webs 7, between layer 8 of a thermoplastic material the other. A particle finish layer is also bonded to glass.

of those of a

Figure 4 shows the structure of Figure 3 when cooled after being subjected to temperature and pressure, in a mold molding process. The thermoplastic layer 8 filled the interstices of the fiberglass rim 7 to form an integrated, base structure 10, a continuous surface layer 11 being formed simultaneously from the particulate layer 9.

The character of the particulate layers 3 and 9 in Figures 1 and 3 can vary depending on the character of the substrate to which they are applied and the final result in the molded article. Thus, particles of a mineral filler material mixed with a sufficient amount of a binder may be suitable in some cases to adhere to the surface of the substrate. During the molding process, the filling material acts to increase the viscosity of the thermoplastic close to the surface of the base layer to resist the overflow by the fibers

Al ternat i vaniente, thermoplastic particles can be used which, when melted, have the effect of enriching the surface parts of the laminate with thermoplastic, and prevent the transfer of fibers. Again, mineral particles coated with thermoplastic can be used alone, or in combination with thermoplastic particles, to form the surface layer. Suitable particulate materials are described in the International Publication (PCT) ΝΘ. WO 88/00608 and UK Patent Application NQ. 2 179 7665 A. The particulate material, added as a surface layer can also include particulate antioxidant material.

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-11 Referring now to Figure 5, this shows a sequence of operations for the manufacture of a fiber-reinforced plastic molded. As will be explained subsequently, the surface finish layer, in particles, can be applied at various points in this sequence.

Figure 5 shows a Fourdrinier 12 screen in which an open, permeable, sheet-like structure is formed from refined fibers and particulate plastic material, generally described in United States Patent No. 4 734 221. The sheet structure passes through a heater / dryer 13, as described in this patent, and is then treated in one of three different ways. It can be consolidated into a double belt press 14, again, as described in United States Patent No. 4,734 321. Alternatively, the permeable sheet can be heated in a heater 15 and then consolidated and re-expanded in a wedge roller system 16, of the type described in European Patent Application No. 87306602 (Publication No. 0255316). This system produces a rigid but permeable sheet. As a second alternative, the sheet-permeable material produced on the Froudrinier 12 screen, can be wound as shown in 17, for later use without any intermediate treatment.

It will be seen that the proposed alternative process will result in a consolidated impermeable sheet, a semi-expanded impermeable sheet or a flexible permeable (coiled) sheet. By using guillotine 18 these three forms of material can be converted into sheets as shown in 1.9.

The sheets 19 are then fed, sequentially, through a preheater 20, before molding into a mold 21, to form a fiber-reinforced mold 22. The type of preheater ^- 20 used, depends on the nature of the leaves to be heated. For waterproof sheets, the use of infrared heating is appropriate, but when the sheets are permeable, flat bed or air circulation heaters can be used. Microwave heating can also be used for all leaf shapes.

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-12It may be described, a surface layer of material may be applied at various positions in the above sequence of operations depending on the optimum position, either on the nature of the foam, particles, particulate material to be applied or on the sheet to which it is applied. applied.

6 Figure 6 shows a Fourdrinier screen 30 associated with a multiple flow box 31. The flow box 31 feeds a mixture of fibers and particulate plastic material, the web 30 through section 32 and a foam material, to the upper surface of the web thus deposited through a second section 33. The base and surface layers 34 and 35, thus formed, are drained simultaneously through the web.

Figure 7 shows a configuration similar to that of Figure 6. In this case, however, separate flow boxes 36 and 37 are provided to deposit, respectively, the base and surface layer, from foam dispersions.

Figure 8 shows a configuration for use in applying a surface layer from an aqueous dispersion. Here, the base sheet 34 is deposited from a foam dispersion through the flow box 36, and the surface layer is applied from an aqueous dispersion by a curtain coating device 37.

Figure 9 shows a configuration in which layers 34 and 35 are deposited by a multi-layer cargo box of the type sold by KMW or Beloit under the trademark Converflo. The base layer 34 is deposited from a foam support fed through the lower blade 38 of the cargo box and the surface layer of particulate material is deposited from the upper blade 39 of the cargo box.

Figure 10 shows a usable system inlet. The dryer or pre-dryer system shown in Figure 5 comprises a screw feeder by weight control or a belt feeder 40 which can be of the type sold by K ~ Tron Soder AG, of Switzerland. The screw feeder supplies the material

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-13 in particles to a vibrating tray 41 which, in turn, deposits the material on a distribution platform 42 from which it falls to the web 43. Subsequent heating in the dryer or heater causes the particulate material to bind to the web.

Figure 11 shows a similar system in which materials, such as thermoplastic fibers 45, are deposited by a vibrating screw feeder by weight control 46 for platform 47, identical to platform 42, and thus for web 48. again, the fibers are connected to the web during passage through the dryer or heater.

The systems shown in Figures 10 and 11 can also be used at the outlets of the dryer or heater, as long as the temperature of the emergent base material is sufficient to cause the particulate material to fuse therein.

Figure 12 shows a system for applying the particulate material to a porous web inside a dryer or heater. Air from a fan circulates through a conduit circuit 51 which includes a heating zone 52 and a heating chamber 53 through which web 54 passes. A screw feeder 55 feeds the particulate material 56 to the above heating chamber of the web, the material being distributed over the web by turbulence of the air and simultaneously connected to the web to form a superficial layer 57.

As shown in figure 13, a double belt laminating machine is employed to produce a web 72 which is composed of a resin and fiberglass craze. In the described process, the fiberglass blankets 71 and 71 'are fed between two straps of? lamination 73 and 74. The molten resin 75 is fed between the two blankets 71 and 71 'from an adjustable slot 76, located along the length of an extrusion die 77. The particulate material 78 is also distributed in the surface of the mat 71 'by a powder feeder system 79, which can be of the type shown in Figure 10, above.

Belt 74, as it passes around cylinder 81, is preheated by a heater 83, before engaging the

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AJBB / SPY / W.147 aZ-14pressure and heating 85. In a similar way, the belt 73 is preheated by the heater 86 before it passes through the pressure roller 85. The pressure and heating roller is equipped with heaters 88. Pressure is applied to laminate 72 by applying tension to belts 73 and 74. The tension applied to belts 73 and 74 results in the application of radial forces to the blanket and resin composite. The resulting radial forces and pressures help to saturate the blankets 71 and 71 'with resin when coupled with the applied heat as the tension is applied. The roller 94 applies tension to the belt 73 and the roller 95 applies tension to the belt 74. The material, such as a compact sheet of resin and fiberglass, that results from the passage of the materials around the pressure roller 85 is then passed to a cooling roller 90 between the straps 73 and 74 and, during its passage over this roller, it is cooled parially, but not completely solidified. The roller 90 is equipped with a cooler 91 to reduce the temperature of the straps and the resin. The sheet, after leaving the roll 90 between the straps 73 and 74, passes through another elongated cooling zone 92, to further reduce the temperature of the straps 73 and 74, to cool and further solidify the blankets and resin in the sheet 72. The strap 73 is then flexed over the roll 95 to return to the tension roll 94 and the strap is re-sent, over the roll 95, to the roll 81, with the product 72 being removed at the point where the straps 73 and 74 separate.

The particulate material 78 can be thermoplastic, an antioxidant hardening plastic, or mixtures of a mineral, a hot or such materials.

fiberglass, particles, (b) or compositions of When incorporated into the produced sheet it has the effect, for the reasons explained above, of preventing the fibers from crossing the surface.

A granular filler material suitable for incorporation into a composition for use in coating the surface of a blanket-reinforced thermoplastic material comprises (a) an inorganic material of 0.1% to 10% by weight based on the weight of the material inorganic fine carbon black, and (c) sufficient composition of natural or synthetic latex, to provide 1%

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-15 to 10%, by weight, of elastomeric solids, based on the weight of the inorganic material, and where the grains have diameters in the range of 0.01 mm to 0.1 mui.

A composition, for use in coating the surface of a thermoplastic material reinforced with a fiberglass mat, according to the invention, comprises an aqueous suspension of a polypropylene powder, a granular filler material, according to said aspect of invention, and a foaming agent. Vant. moreover, the composition also includes solids of natural or synthetic latex, in addition to those present in the granular filler material.

The size of the grains that make up the filling material is important because the grains need to be relatively fine so that the inorganic material, latex solids and carbon black, which make up the granules, are dispersed in a substantially uniform manner in the surface layer of the thermoplastic material reinforced by a fiberglass mat. Also, if the granules are relatively fine, it is less likely that the carbon black is in an aggregate state, thus obtaining a more intense and more uniform black pigmentation.

The granules of the filler material may also contain from 0.1% to 10% by weight, based on the weight of the inorganic material, of an antioxidant for the polypropylene. The antioxidant can conveniently be hay type! prevented from dyeing.

particulate inorganic material can be kaolinitic clay (eg kaolin or plastic clay), calcined kaolinitic clay, calcium carbonate, aluminum and calcium silicate (eg the natural silicate known as wol1astonite), bauxite, talc, tri -alumina, silica, magnesium carbonates and hydroxides (eg natural hydrotalcite), dolomite (ie double calcium carbonate and natural magnesium), calcium sulfate (eg gypsum) and titanium dioxide. The inorganic material can be natural or synthetic and, in particular, both forms, natural and synthetic, of calcium carbonate, aluminum and calcium silicates, silica, carbonates and magnesium hydroxide,

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-16 pupiline trihydrate, calcium sulfate and titanium dioxide are within the scope of this invention. When the material is synthetic, it can be precipitated (as with calcium carbonate, silica and titanium dioxide). More generally, it has been found that the inorganic materials that are most suitable for use in this invention are those that can be considered as white inorganic materials. (It should be noted that the term white used in connection with inorganic material does not mean that the mineral necessarily has a pure white color, but is substantially free of any * strong hue). Many of the inorganic materials that may be non-white in the present invention should be crystalline. Of not more than 50 microns preferably used, and more preferably, not more than 30 microns in diameter.

The granules of the filling material are preferably prepared in the form of hollow microspheres and can, very suitably, be produced by spray drying an aqueous solution. Most preferably, the solution is in a spray-nozzle-type automatic dryer, since this type of spray-dryer allows control over the size of the microspheres produced in the desired 0.01 mm to 0.1 mm. A suitable aqueous suspension can be prepared by the joint dispersion in water that contains a dehydrated, good gamma feed may preferably be a carbon black, anti-oxidant.

dispersing agent, inorganic material, and a latex composition and, optionally, a

A preferred process for the preparation of the filler granules comprises the following steps:

a) the fine carbon black is mixed with water containing dispersing agent to form a suspension, preferably containing from about 5% to about 35%, by weight, of carbon black;

of the uin of in

b) a suspension, preferably containing 50% to 65%, of a dry weight of a white inorganic material dispersing agent for the inorganic material, is on a base and a mixture

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-17with the carbon black suspension formed in step a), in such proportions that the amount of carbon black is preferably in the range of 0.1% to 10%, on a dry weight basis, based on the weight of the inorganic material;

is mixed with the suspension of inorganic / carbon black material _f formed in step b), a sufficient amount of a composition of natural or synthetic latex to originate from 1% to 10%, by weight, of latex solids, based in the weight of the inorganic material, and the mixed suspension formed in step c) is spray dried to form hollow microspheres of substantially dry material, with diameters in the range of from 0.01 mm to 0.1 mm.

In step a) the dispersing agent can be, for example, a water-soluble salt of poly (acrylic acid), poly (meta-methyl acid) or a copolymer containing 10% to 80% by weight of monomeric aerilonitrile units or meta-acrylonitrile and 90% to 20% by weight of monomer units of acrylic acid or meta-acrylic acid. The average numerical molecular mass of the water-soluble polymer, and preferably not more than about 10,000. The amount of dispersant used is preferably in the range of 0.1% to 5% by weight, based on dry charcoal black weight.

In step b) the dispersing agent for the inorganic material is advantageously a water-soluble salt of poly (acrylic acid) or poly (meta-methyl acid), with an average numerical molecular mass of not more than 10,000. Preferably, the dispersing agent used for the inorganic material is the same used for carbon black. The amount of dispersing agent used is preferably in the range of 0.05% to 0.5% by weight, based on the weight of the dry inorganic material. The inorganic material does not require any chemical pretreatment other than dispersion with a dispersing agent.

In step c) the latex can be one of a natural rubber, or a natural rubber that has been replaced with groups

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-18 functional, or a synthetic rubber such as a styrene-butadiene rubber (SBR). Other suitable matrices include those formed from acrylic copolymers (whether elastomeric or non-elastomeric, although elastomeric are preferred) and non-elastomeric materials such as vinyl polyfacetate and vinyl acetate copolymers.

The acrylic copolymer can be a copolymer of a lower alkyl ester of an acrylic acid with a lower alkyl ester of methacrylic acid. Particularly preferred are the copolymers of ethyl acrylate and methyl methacrylate. Also suitable are co-polymers of one or the other or both of a lower alkyl ester or acrylic acid and a lower alkyl ester of methacrylic acid with another monomer chosen from vinyl acetate, styrene, acrylonitrile or their mixtures. The alkyl chains of the lower alkyl esters of acrylic acid and methacrylic acid preferably have one to four carbon atoms.

Vinyl acetate copolymers can be formed by copolymerizing vinyl acetate with a copolymerizing monomer chosen from a lower alkyl ester of acrylic acid, a lower alkyl ester of methacrylic acid, styrene, acrylonitrile and mixtures thereof .

The latex composition, which is a stabilized suspension of polymer particles in water, typically contains about 40% to 60% by weight of solids. The latex can be stabilized with the help of a surfactant or a water-soluble colloid, although a surfactant is normally used, as it usually gives a latex with lower viscosity.

The mixed suspension formed in step c) may also contain an antioxidant, suitably, of the hindered phenol type that does not dye. Conventionally, such an antioxidant is mixed with water to form a suspension containing about 40% by weight to about 60% by weight of the dry antioxidant, and the suspension mixed with the suspension formulated in step c), in proportions such as to give 0.1% to 10% by weight of the dry antioxidant,

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-19based on the weight of dry inorganic material.

In step d) the spray dryer is most preferably thermal degradation of the carbon black.

Orifice temperature, preferably less less than 350 ° C, the elastomeric material admi SSAO than 400 ° C to prevent combustion or ^e 'to

of

The granules of the filling material, from; according to the invention, they can be incorporated into a coating composition for a thermoplastic material reinforced by a fiberglass mat, adding water, granules and polypropylene powder in proportions ranging from 5 parts, by weight, from granules to 95 parts , by weight, of; polypropylene, 95 parts by weight of granules, to 5 parts by weight of polypropylene. Preferably, then, sufficient latex composition of the types described above is added to give 0.5 to 10 parts by weight of latex solids per 100 parts by weight of granules and polypropylene. Finally, a foaming agent is added: it can be anionic, for example sodium dodecylsulfonate, or non-ionic. The ingredients are then vigorously mixed to form a foam which is conveniently applied, by means of a curtain coating device, to the thermoplastic composition reinforced by a fiberglass mat on the Fourdrinier paper making machine. The invention is further illustrated by the following example.

Example

A carbon black powder with an average particle diameter of 0.02 millimeter was dispersed in an amount of water to form a suspension containing 20% by weight of carbon black, being dissolved in water 2% , by weight, based on the weight of the carbon black, in a sodium polyacrylate dispersing agent, with a numerical molecular mass of 1680. The carbon black suspension was then added to a suspension containing 60 % by weight of a kaolinitic clay of filling material grade for paper and 0.2% by weight, based on the weight of dry kaolin, of the same dispersing agent used for carbon black.

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-20The kaolinitic clay had a particle size distribution such that 20% by weight consisted of particles with an equivalent spherical diameter greater than 10 microns and 35% by weight consisted of particles with an equivalent spherical diameter less than 2 microns. The carbon black suspension was mixed with the kaolin suspension in proportions such that the amount of dry carbon black was 5.6% by weight, based on the weight of the dry kaolinitic clay.

We then added to the kaolin / carbon black suspension thus formed, first, a latex containing 50% by weight of an elastomeric acrylic copolymer of ethyl acrylate and methyl inethacrylate, were such proportions that the amount of the dry elastomeric copolymer is 5.6% by weight, based on the weight of the dry kaolinitic clay; and, second, a suspension containing 50% by weight of a non-dyeing antioxidant, of the hindered phenol type, in such proportions that the amount of the antioxidant was 1.1% by weight, based on the weight of the dry kaolinitic clay.

The resulting mixed suspension was spray dried in an automatic nozzle dryer spray where the temperature of the feed hole was 300 ° C and the nozzle adjustments were such that the solid components of the mixture were recovered in the form of hollow microspheres. , dry, with diameters in the range of 0.01 to 0.1 mm.

Two coating compositions were prepared: in each case quantities of granules and polypropylene powder were stirred in the water, followed by sodium dodeci1-sulfonate as a foaming agent and an amount of poly latex (acetate in each case the vinyl ingredients) . They were vigorously mixed if a foam was produced which was applied to the upper surface of a polypropylene material reinforced by a fiberglass mat, on the moving wire mesh of a Fourdrinier paper-making machine.

The weight by weight for two compositions contained, respectively, 30 parts, of the granules, the filling material for 70 parts, the polypropylene powder and 50 parts, by weight, of the

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-21 granules of the filling material for 50 parts by weight of polypropylene powder. In each case, after the coated glass fiber reinforced thermoplastic material was cut into pieces, and the pieces were stacked and pressed at 200 ° C between steel plates and allowed to cool in the press, the resulting sheet material had a smooth surface with a uniform black color and no protruding glass fibers.

Claims (10)

1 - Process for the production of a permeable sheet of glass fiber reinforced thermoplastic material, for molding a shaped product, characterized by comprising the bonding to the sheet of a surface layer of a particulate material, compatible or inert in relation to the thermoplastic content of said sheet and which acts to improve the surface finish when the sheet is subsequently heated and molded into a die under pressure. Process according to claim 1, in particles being a mineral characterized by filling the material. Process according to claim 2, characterized in that the mineral filler material is clay, carbon black or titanium dioxide, calcium carbonate, a thermoplastic, a hot-hardening plastic, an antioxidant material, a pigment or a mixture of such materials. Process according to claim 1 or 2, characterized in that the particulate material is, or includes, an inorganic filler with a polymeric coating. Process according to claims 1, 2 or 3, characterized in that it comprises applying the particulate surface layer, by aqueous coating of a dispersion of the particulate material. Process according to claims 1, 2 or 3, characterized in that a surfactant is added, and the dispersion is stirred under turbulent conditions to form a foam which is then applied as a coating. Process according to claims 1, 2 or 3, characterized in that the particulate material is applied as a dry powder one 24. JUL. nineteen ninety Lisbon, By THE WIGGINS TEAPE GROUP LIMITED OFFICIAL 71 306 AJBB / SPY / W.147 -23 characterized by associating (a) a particulate inorganic material, (b) from 0.1% to 10% by weight, based on the weight of the fine inorganic material, of fine carbon black, with (c) an amount enough of a composition of natural or synthetic latex to provide 1% to 10% by weight of elastomeric solids, based on the weight of the inorganic material, and the granules having a diameter of 0.01 mm to 0.1 mm . ') 9 - Process for the preparation of a composition for use in the coating of a thermoplastic material reinforced with a fiberglass mat, characterized by making an aqueous suspension of a propylene powder, of a granular filling material, according to the claim 8, and a foaming agent. Process according to claim 8 or according to claim 9, characterized in that the particulate inorganic material is a kaolinitic clay, a calcined kaolinitic clay, a calcium carbonate, an aluminum and calcium silicate, bauxite, talc, mica, alumina trihydrate, silica, a magnesium carbonate or hydroxide, dolomite, calcium sulfate or titanium dioxide. Process according to claim 8 or 9 or 10, characterized in that the inorganic particles have a diameter not exceeding 50 microns.